Improvement in prison-gratings



E, MAY.

Improvement in Prison Gratin'gs.

lnvenl'ar Wi. 'ne s s e s sind@ tsis EDWIN MAY, OF INDIANAPOLIS, INDIANA.

Letters Patent No. 114,584, dated May 9,1871.

'INI PRQVEM ENT IN PRISON-GRATINGS.

The Schedule referred. to in these Letters Patent: and making pau-t of the same.

I, EDWIN MAY, of Indianapolis, in the county of Marion, State of Indiana, have invented certain Improvements in the Construction of Prison-Gratings, of which the following is a speeication.

Nat'ufre and Objects of the Invention.

My invention relates to prison-gratings; and

It consists in the construction and arrangement of a saw and file-proof clamp-guard to the bolts or rivets, which is composed of soft iron and hard steel, or soft and hard steel, in combination withthe form and arrangement of the grate-bars, and the manner of boltiug or riveting them together, said bars and rivets or bolts being made of a similar material, the object being to present still further obstacles to the bolts or rivets being sawed o".

Description of Accompanying Drawing.

General Description.

B are the grate-bars, made of hardened steel, or, preferably, composed of either hard and soft steel or soft iron and hardened steel, formed as'shown iu figs.

At the place where the bars are brought near each other so as to be bolted or riveted together I place a plate or clamp-guard, A, formed as shown, and constructed of any saw or file-proof material, similar to the bars B.

The outer ends of' this clamp-guard are shouldered, as shown, so as to prevent the bars from being moved laterally; and this projecting shoulder or cap also renders it more diicult to be sawed iutoiu order to reach the rivet or bolt O.

The bolts C pass through both bars B and the guard A, as shown.

The advantage of this construction of the gratings is the perfect security offered over the old method of common iron window-grates however large the bars they could be easily sawed oli', and the larger the bars the more obstruction to light and ventilation.

The peculiar form and use of my clamp-guard will be more readily understood when it is known that the bars have to be hardened before being riveted together, as the grating completed would be too large aud unwieldy for anyheat to be brought to bear ou it in order to temper it for the hardening process, and being riveted together with the rivets red hot in order to swage them down to ill the tapered or rose-drilled holes in the bars. This will leave the rivets, after the grating is all built up, in a soft or untempered state, and, unprotected, would not resist a saw or lile, yet in its strongest state forsecurely holding together the bars within the clamp-guard and the clamp-guard between the bars; the head of the rivets or bolts outside of the bars may then be cut oli' and no separation will take pla'ce, as the taper-drilled holes form a. dovetail-rivet or bolt.

The hars and clamp-guard bengboth saw and iileproof, the peculiar shape of the clamp-.guard eiiectually protects the rivets or bolts Vfrom the saw or le, rendering the whole arrangement proof .against any i of the common devices of prison-breakers to saw out.

This form of grating can be used for prison-doors and inside-corridor partitions.

I make no claim to tbe combined steel and iron and the ,taper-shaped or dovetailed bolt; but

What I do claim as my invention is- The clamp-guard A, in combination with the bars B and bolt C, all constructed and arranged substantially as and for the purposes set forth.

EDWIN MAY.

Witnesses:

WM. H. WEEKS, A O. F. MAYHEW. 

